1. Field of the Invention
The present invention relates to a recording element substrate, an inkjet head, and a production method of the inkjet head. More particularly, the present invention relates to the ink jet head for holding and fixing a recording element substrate to a supporting member, and a production method of the ink jet head.
2. Description of the Related Art
An inkjet recording apparatus discharges ink in a minute droplet state from a plurality of discharge ports arrayed on an inkjet head, and records an image.
Generally, as a recording element substrate provided in a inkjet head, a silicon single crystal substrate having a clipping orientation of <100> (hereinafter refereed to as a silicon substrate) is used, and the silicon substrate is provided with a discharge pressure generating element for discharging ink. Further, to supply ink to the discharge pressure generating element, a supply port is provided, which penetrates the silicon substrate, and an ink flow path is formed from the supply port to the discharge pressure generating element. The ink, by pressure applied from the discharge pressure generating element, flies from the discharge port provided in the ink flow path, impacts on a recording surface such as a printing paper, and a desired image is obtained.
A through hole corresponding to the supply port of the recording element substrate is provided in the supporting member for holding and fixing the recording element substrate, and forms an ink flow path. A protrusion is provided on a second surface of the recording element substrate which is opposite to a first surface provided with the discharge pressure generating element. A leading edge of the protrusion and the supporting member are bonded by using an adhesive.
FIG. 7 is a perspective view illustrating a partially broken recording element substrate 1, which discharges multi-color inks, e.g., cyan, magenta, and yellow. FIG. 8 is a cross-sectional view illustrating one example state in which the recording element substrate 1 is fixed on a supporting member 13.
In FIG. 7, supply ports 10 are formed on a silicon substrate 2 corresponding to each color, along discharge port arrays 18 with discharge ports 12 arranged in parallel. As illustrated in FIG. 8, through holes 16 are also formed in the supporting member 13 corresponding to the supply ports 10. In a conventional structure of the recording element substrate, an adhesive for bonding the silicon substrate 2 and the supporting member 13 is used to seal a contact part of the supply port 10 and the through hole 16.
In recent years, customers have demanded an inkjet recording apparatus which shows high image quality, high brilliance, and high throughput with a low price. One method for lowering the cost of the inkjet recording apparatus is to lower a production cost of the inkjet head.
One method for lowering the cost is to increase the number of a silicon substrate taken from one silicon wafer. More specifically, an interval between the supply ports is narrowed to reduce the size of the silicon substrate, so that the number of the silicon substrate taken from one silicon wafer is increased.
However, as illustrated in FIG. 8, when the interval between the supply ports is narrowed, a bonding surface between the silicon substrate 2 and the supporting member 13 becomes small, so that it becomes difficult to coat an adhesive on the bonding surface. Further, since the bonding surface does not have a sufficient area, it becomes difficult to maintain sealing reliability of the adhesive. When the sealing reliability lowers, ink leakage from the bonding surface occurs, an amount of ink discharging from the discharge ports becomes irregular, so that a recording quality may degrade. In an inkjet head discharging multi-color inks, different color inks may be mixed, so that an image quality and definition may degrade.
To solve these problems, Japanese Patent Application Laid-Open No. 11-192705 discusses a sealing method other than use of an adhesive to increase adhesive strength between the recording element substrate and the supporting member. According to the method discussed in Japanese Patent Application Laid-Open No. 11-192705, a solder bump is used to weld the recording element substrate with the supporting member and form a fluid partition wall which partitions ink flow paths of different colors. However, since the solder bump is generally formed with a pattern of several-hundred microns, the size of the solder bump causes a trouble when the boding surface of the recording element substrate and the supporting member is to be narrowed.
As a method for sealing other than the method using an adhesive or a solder, a bump can be formed in a fine pattern and the recording element substrate is welded with the supporting member. As a general technique for forming the bump, there is a metal plating method as represented by a formation of a gold bump. However, to bond the supporting member and the bump formed on the recording element substrate by the metal plating method, it is necessary to secure a flatness of the bonding surface or to form a bump which has an enough height so that the flatness is negligible.
Particularly, when the supply port and the protrusion are formed on the silicon substrate, laser processing is used. However, in such a case, chipping and burrs are generated so that flatness is lowered. Generally, planarization processing such as chemical mechanical polishing (CMP) is indispensable for increasing flatness of a bonding surface. Further, the plating needs to be performed for a long time to form a high bump. Both of the planarization processing and the forming of the high bump increase production cost in acquiring a desired configuration.